Each person is unique and his hair is unique as well. As well as hair quantity, density, thickness, color and the time span of their life for each person is different too. Children’s hair is changing more rapidly than adults, the hair grows faster in summer than in winter, blondes have more hair, but they are thinner; redheads  have less hair but they are thicker, and so on. An average adult has 90-150 thousand hair on his head. An average adulta has roughly about 5 million hair follicles. Of these only 1 million applies to head skin and out of those only an average of 150 000 go to hairy head part and this final number depends on your specific natural hair color. Hair follicles are recognized as an individual formation developed by skin with all the subsequent maintaining processes that interact with the skin and epidermal components. Hair follicle volume decreases with age. Hair has an average growth of 10-15 mm per month, sometimes about 20 mm (about half a millimeter per day), but as it reaches a certain length it slows down in growth almost per half.  The hair has an average life expectancy of 2-6 years, but it can be sometimes much more. With normal hair growth an average of 80% of the hair follicle are in growth phase and remaining 20 percent are in a regression (falling out) phase. In fact, there are differences in hair growth depending on their owner ethnic origin. For length to shoulder the hair is about two years old, to the waist (80-90 cm. in length) hair is growing approximately seven years. Talking max figures most likely the hair can grow from 7 to 30 years. Hair grows all the time: the new cells are formed, get mature and "fall asleep", pushing the hair forward. What may be the maximum length of hair? If you are not going to cut your hair entirely you can grow them quite long, although there is a certain limitation of the maximum length due to the possibility of the scalp to produce hair. Hair growth is regulated by our genes. Some people have short hair genes, others can grow hair much longer. Statisticly for an average human hair in the active growth phase, the max life span is about 2000 days. And the hair growth rate during the day - 0.35 mm. So it is easy to calculate that the max average length of hair grown can reach 80cm. But, once again, sometimes hair may be significantly longer.